why NSTimer works just once in swift

Question

I have a http request, and if I receive the response correctly, then I want to start a timer that fires a function each second. That function is also a http request.

this is my code to fire the timer

    if let data = data {
        do{
            let resultJSON = try NSJSONSerialization.JSONObjectWithData(data, options: [])
            requestClient.id = resultJSON["id"] as! Double
            self.timerResponse = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "checkIfThereAreResponeses", userInfo: nil, repeats: true)
            self.timerResponse!.fire()
        }catch{
        }
    }

as you see, I'm calling a function called checkIfThereAreResponses

In that function, i have a print statement, and that print statement is being printed just once, though my timer supposed to work each 1 second

what missing i have?

And this is the function

 func checkIfThereAreResponeses(){
    if (requestClient!.id != nil) {
        let url = NSURL(string: "http://localhost:blablabla")
        let request = NSMutableURLRequest(URL: url)
        request.HTTPMethod = "POST"

        let session = NSURLSession.sharedSession()

        task = session.dataTaskWithRequest(request, completionHandler: {(data, response, error) in
            if let error = error {
                print("error = \(error)")
            }



            if let data = data {
                do {
                    let resultJSONArray = try NSJSONSerialization.JSONObjectWithData(data, options: []) as! NSArray
        bla bla bla

                }catch {
                    print("no responses yet = \(error)")
                }
            }
        })
        task!.resume()
    }else {
        print("not yet ")
    }
}

the print that i receive JUST ONCE is the no response yet

Answer 1

If you have this code in completion handler, it is recommended NSTimer is running in the main thread so this could be the reason. You might need something like:

dispatch_async(dispatch_get_main_queue(), {
    // Your timer logic here
})

Apple docs say:

Timers work in conjunction with run loops. To use a timer effectively, you should be aware of how run loops operate—see NSRunLoop.

(NSTimer)

The NSRunLoop class is generally not considered to be thread-safe and its methods should only be called within the context of the current thread. You should never try to call the methods of an NSRunLoop object running in a different thread, as doing so might cause unexpected results.

(NSRunLoop)